1. Field of the Invention
The invention is related to polysulfones that contain first and second different sulfone units as the only repeating units. The first of the repeating sulfone units of the polysulfone is a polyphenylsulfone unit based on a diphenyl sulfone and a biphenol. The second repeating unit of the polysulfone is a fluorinated polysulfone based on a diphenyl sulfone and a hexafluorobisphenol A. The invention further relates to methods of manufacturing the polysulfones, compositions containing the polysulfones, methods of using the polysulfones, and articles made from the polysulfones.
2. Description of the Related Art
Polysulfones are polymers that have repeating or recurring —SO2— groups. The term “polysulfone” is used generically to describe any polymer containing repeating or recurring units of one or more diamyl sulfone groups (e.g., monomers) of general formula —(Ar—SO2—Ar)—, where Ar is a substituted or unsubstituted aryl group such as a phenyl, biphenyl, bisphenol or any other aryl group containing an aromatic hydrocarbon or hetero-aromatic ring.
Polysulfones include repeating or recurring units of a diaryl sulfone such as diphenyl sulfone (e.g., (—C6H4)—SO2—(C6H4)—) bonded to a diphenol such as biphenol (e.g., HO—(C6H4)—(C6H4)—OH). A single diphenyl sulfone group is shown below.

Commercially important polysulfones generally contain only a single type of diaryl sulfone group. Most polysulfones do not include sulfone groups other than a diarylsulfone (e.g., the only —SO2— groups is a diaryl sulfone group). Likewise, most polysulfones contain only a single type of diphenol such as biphenol or bisphenol A.
Well known and commercially available polysulfones include the polysulfone identified herein as PSU. PSU contains reacted units of diphenyl sulfone and bisphenol A (BPA). PSU is available commercially from Solvay Advanced Polymers (i.e., under the tradename UDEL®). The UDEL® polysulfone includes polymerized groups of diphenylsulfone and bisphenol A. The structure of the repeating unit of a UDEL® polysulfone, made by condensing bisphenol A and 4,4′-dichlorodiphenyl sulfone, is shown below. PSU has a high glass transition temperature (e.g., about 185° C.) and exhibits high strength and toughness.

RADEL® R polyphenylsulfone is another polysulfone available from Solvay Advanced Polymers. RADEL® R polyphenylsulfone is made by reacting units of 4,4′-dichlorodiphenyl sulfone and 4,4′-biphenol. A polyphenylsulfone, such as RADEL® R, that includes reacted groups of biphenol and diphenyl sulfone is identified herein as PPSU. The chemical structure of a RADEL® R polyphenylsulfone is shown below.

Other polysulfones include co-polymers having at least two different types of sulfone and/or diphenol groups. RADEL® A polyethersulfones, available from Solvay Advanced Polymers, include a polyethersulfone portion made from repeating or recurring groups of formula (—Ar—SO2—Ar—O)n and a relatively lower amount of a polyetherethersulfone portion of formula (—Ar—SO2—Ar—O—Ar′—O—)m, where the polyethersulfone portion and the polyetherethersulfone portion are bonded to one another. The chemical structures of a polyether sulfone and a polyetherethersulfone portion of a RADEL® A co-polymer are shown below.

Polysulfones are typically amorphous and do not melt crystallize. One substantial advantage of polysulfones is their transparency. Due to their high strength and heat resistance, certain polysulfones may be used in high-stress environments where other transparent polymers such as polycarbonate may degrade or may otherwise be unsuitable. Polysulfones are particularly well suited for aircraft applications where lightness and strength are key properties. Polysulfones are used in many aircraft applications including, for example, passenger service units, staircases, window reveals, ceiling panels, information displays, window covers, ceiling panels, sidewall panels, wall partitions, display cases, mirrors, sun visors, window shades, storage bins, storage doors, ceiling overhead storage lockers, serving trays, seat backs, cabin partitions, and ducts. Transparent articles such as windows, lighting fixtures and partitions are especially well suited for polysulfones and compositions containing polysulfones.
Further advantages of polysulfones include good chemical resistance, such that polysulfones are able to withstand exposure to the types of cleaning fluids used in the aircraft industry; processability in the melt phase including injection molding and extrusion; and ease of colorability.
Polysulfones undergo thermal degradation, e.g., burning or combustion, with low smoke emission and low thermal emission. To be permitted for use inside aircraft, engineering thermoplastics, including polysulfones, must meet certain requirements for flame resistance (e.g., flame retardency) and heat release during combustion. Air worthiness standards issued by the U.S. government and codified in Title 14 Code of Federal Regulations (51 Federal Register 26206, Jul. 21, 1986 and 51 Federal Register 28322, Aug. 7, 1986) provide flammability standards based on heat calorimetry testing. The air worthiness standards of Title 14 of the CFR are incorporated by reference herein in their entirety.
The heat calorimetry testing methodology used to determine whether an engineering thermoplastic meets U.S. government air worthiness standards were developed at Ohio State University and are known as the OSU Flammability Test. The OSU tests measure the two minute total heat release (THR) and peak heat release (HRR) in kilowatt minutes per square meter of surface area, i.e., kW·min/m2, and kilowatt per square meter of surface area, i.e., kW/m2, respectively, for the first five minutes of a burn test under the conditions of the OSU testing.
The most recent air worthiness standards, enacted in 1990, for engineering thermoplastics require that both THR and HRR have values of 65 or less for both THR and HRR. Some polysulfone materials such as PSU meet current air worthiness standards; however, when used as a blend with other polymers the THR and/or HRR thresholds may be exceeded. Moreover, in the future, air worthiness standards are likely to become stricter, e.g., leading to a further lowering of permissible maximum THR and/or HRR values. Further improvements in the flame resistance/flame retardancy and thermal release properties of polysulfone materials are desirable to improve aircraft safety and to permit continued use of polysulfones in the aircraft applications.
Of the polysulfones that are presently commercially available, polyphenylsulfone (PPSU) in particular provides excellent performance for aircraft applications where transparency is required. Still, the heat release properties of polysulfones that are currently commercially available are inferior to the heat release properties of other engineering thermoplastic compositions, especially opaque plastic materials and/or blends that contain one or more conventional flame retardants.
Conventional flame retardants such as triphenyl phosphate or melamine cyanurate are often mixed with conventional engineering thermoplastics to improve heat release properties and to reduce flammability. Such conventional flame retardants may be added to polysulfone compositions; however, the resulting compositions often exhibit significantly impaired transparency. For example, when added to a polysulfone, such flame retardants may not be miscible with the engineering thermoplastic and consequently impart haze and/or an opaque appearance to the polysulfone. Common flame retardants, including inorganic additives such as TiO2, ZnO or Zinc borate, provide improved flame retardancy only at high loading levels with a concomitant negative effect on weight, processability and optical properties.
Fluorocarbon resins such as polytetrafluoroethylene have been used to improve the flame retardance, flame resistance and thermal release properties of conventional engineering thermoplastics such as polycarbonate. Fluorocarbon resins have also been used in combination with polysulfones. For example, U.S. Pat. No. 5,204,400 discloses flame retardant thermoplastic compositions comprising the poly(biphenylethersulfone) of formula:
wherein R1 though R4 are —O—, —SO2—, —S—, —C(O)—, with the provision that at least one of R1 though R4 is an —SO2— group and that at least one of R1 though R4 is —O—; Ar1, Ar2, Ar3 are arylene radicals containing 6 to 24 carbon atoms. The compositions further contain anhydrous Zinc borate and a fluorocarbon polymer present in the form of finely divided solids.
U.S. Pat. No. 5,916,958 discloses compositions comprising a poly(biphenylethersulfone) of formula:
in combination with a fluorocarbon polymer and titanium dioxide. The compositions exhibited enhanced flame retardant characteristics and were described as useful for making aircraft interior parts. The fluorocarbon polymer additive is preferably a polytetrafluoroethylene (PTFE) in the form of a finely divided solid having a particle size of less than about 5 μm.
U.S. Pat. No. 6,503,988 discloses flame resistive compositions containing a flammable thermoplastic resin, a flame retardant, and a polytetrafluoroethylene fine powder comprising particles of 0.05 to 1 μm as an anti-dripping agent. Polysulfone resins are mentioned as suitable flammable thermoplastic resin.
U.S. Pat. No. 6,482,880 discloses poly(biphenylethersulfone) resins having improved resistance to yellowing that include PTFE in particulate form.
While such compositions may provide, in some cases, improved flame resistance, flame retardance, and/or reduced thermal release during combustion, the presence of the fluorinated polymer has a strongly negative effect oil the optical and appearance properties of the resulting compositions and leads to a pearlescent and/or opaque appearance. Further, the presence of a fluorinated resin makes the resulting compositions difficult to color. The increased degree of haze and other detrimental optical affects exclude the use of such compositions from applications in which transparency is required.
Thus, there is a need for transparent polysulfone materials and polysulfone-containing compositions that exhibit improved flame resistance, flame retardancy and/or lower thermal release on combustion, which concurrently have excellent optical properties, including transparency.
Polysulfones are also commonly used in the manufacture of shaped articles including purification membranes commonly used in the chemical, food, beverage, water and textile industries such as ultrafiltration, microfiltration, reverse osmosis, and gas and vapor separations membranes as well as in some healthcare treatments, i.e. hemodialysis, blood filtration, etc. . . . One problem with conventional polysulfones used in applications with service requirements including long term exposure to various solvents and chemicals, such as purification membranes, is that they suffer from poor chemical resistance, particularly to certain solvents and chemicals such as hydrocarbons. Furthermore, polysulfones are subject to plasticization when exposed to high concentrations of carbon dioxide that may be encountered during certain gas separations, severely limiting their performance.
There is thus a need for polymeric shaped articles and in particular for fibers, filaments, films, coatings and membranes with an improved chemical resistance.
In addition, purification membranes should be highly selective with respect to various separation problems, exhibit high permeation rates, high mechanical strength, high thermal and chemical resistance. Meeting all these criteria appears tricky because polymer membranes with high permeation rates have generally low selectivities while membranes with high selectivities have low permeation rates.
There is thus also a need for polymeric shaped articles and in particular for purification membranes featuring enhanced flux—selectivity trade-off. This property depends notably on the material's nature and in particular on its density and free volume characteristics. There is thus a need for high permeation rates membranes that encompass also good selectivities.
At least part, and preferably all of these needs, and possibly still other additional needs, are met by the polysulfone copolymer according to the present invention, the polymer composition (C) according to the present invention and the polymeric shaped article (A) according to the present invention comprising at least one part consisting essentially of at least one polysulfone copolymer according to the present invention or the polymer composition (C) according to the present invention.